lnterpretazione geomorfologica di alcuni contatti anomali nella serie UmbroMarchigiana:individuazione di un fenomeno franoso pleistocenico sul versante occidentale della dorsale marchigiana

Geomorphological interpretation of some anomalous contacts in the Umbria-Marche stratigraphic sequence: a Pleistocene landslide on the Western slope of the Marche ridge

Abstract

Some stratigraphic anomalies noted in a limited area of the upper basin of the Chienti River (Central Marche) are interpreted on a geomorphological basis. The overlyings of arenaceous-conglomeratic terrains (Middle Tortonian-Messinian) and of the marly limestones of Bisciaro (Aquitanian-Burdigalian p.p.) to the oligocenic marls of the Scaglia cinerea are interpreted as the result of traslational sliding, which happened in the Lower-Middle Pleistocene, of gigantic blocks, which were formed by fragmentation of masses positioned several hundreds of metres to the east, on a surface slightly dipping south-west. In the genesis and evolution of the phenomenon, the role played by lithostratigraphic, structural and tectonic features of the bedrock and particularly the overlying on plastic levels of rigid masses affected by numerous joints and attitude of the strata, seems evident. At the same time also the Quaternary uplifting had an important role. These last movements, with consequent deepening of the hydrographic network, created, in fact, morphological conditions favourable to the triggering of these large-scale phenomena.